Method and device for heating a rotatably mounted guide casing of a guide roller

ABSTRACT

The invention relates to a method and a device for heating rotatably mounted guide casing of a guide roller for guiding and heating threads. The guide roller has a guide casing which is held on the circumference of an axle support by means of an air bearing. To heat the guide casing, compressed air is heated outside the guide roller and supplied to the air bearing within the guide roller.

The invention relates to a method for heating a rotatably mounted guide casing of a guide roller for guiding and heating threads according to the preamble of claim 1, and a device for carrying out the method according to the preamble of claim 6.

In the manufacture and processing of synthetic threads, it is generally known to wrap one or more threads multiple times around a driven godet casing of a godet so that the thread or threads is/are conveyed through the driven godet casing as the result of wrapping friction. To allow the multiple wrappings on a godet casing, a guide roller having a rotatably mounted guide casing for accommodating the thread wrappings is typically associated with the godet. Such a guide roller is known from DE 26 39 439, for example.

The known guide roller has a rotatably mounted guide casing which is rotatably held on an axle support by means of an air bearing. Multiple heating means are associated with the axle support in order to heat the guide casing and a thread which is guided on the guide casing.

In the known guide roller, for heating the guide casing it is necessary to conduct the energy from the center of the guide roller, in this case, the axle support, to the outer guide casing. The air bearing provided between the guide casing and the axle support represents thermal resistance which results in corresponding energy losses. Therefore, relatively high temperatures must be generated at the axle support in order to heat the guide casing to an external temperature of 100° C., for example. However, such heating in the axle support results in heat deformation, which has an adverse effect on the air bearing. Thus, in terms of energy the known guide roller is very unsuitable for heating the guide casing to a desired surface temperature.

The object of the invention, therefore, is to provide a method and a device for heating a rotatably mounted guide casing of a guide roller, in which the heat energy may be supplied to the guide casing in the most direct manner possible.

A further aim of the invention is to provide a method and a device for heating a rotatably mounted guide casing of a guide roller, which are suitable for retrofitting an unheated guide roller to allow heating of the guide casing.

For a method according to the invention, this object is achieved by heating compressed air and supplying the heated compressed air to the air bearing.

For the device according to the invention for carrying out the method according to the invention, the object is achieved in that a heating means by which compressed air may be heated is associated with the compressed air line outside the guide roller.

Advantageous refinements of the invention are defined by the features and feature combinations of the respective subclaims.

The invention is based on the knowledge that for an air bearing, the compressed air which is supplied between the rotating component and the stationary component is suited as a sliding medium, also in the heated state. In this regard, the compressed air may advantageously be used as a heat transfer medium in order to directly conduct heat energy to the guide casing. The compressed air cushion which is produced for the bearing of the guide casing may also be advantageously produced using the heated compressed air. The invention is therefore characterized in that no additional devices for heating the guide casing are necessary at the guide roller. The compressed air is heated outside the guide roller by a heating means. The heating of the compressed air may thus be carried out in a flexible manner. Thus, for example, the compressed air may be heated directly within a compressed air line, using external heating media associated with the compressed air line.

Particularly advantageous, however, is the refinement of the invention in which the compressed air is heated in a separate compressed air heater by supplying the compressed air to the compressed air heater from a compressed air source. For this purpose, the electric compressed air heater is connected in the compressed air line between the pressure source and a compressed air connection for the guide roller. This allows buffering of the compressed air, which makes intensive heating possible.

Independent of the design of the heating means, it is preferred to use the refinement of the invention in which the compressed air is heated to a setpoint temperature, an actual temperature of the compressed air is detected, and the heating of the compressed air is regulated as a function of a deviation between the setpoint temperature and the actual temperature. For this purpose, a heat control system which is connected to a temperature sensor for detecting an actual temperature of the heated compressed air is associated with the heating means. It may thus be ensured that a predetermined surface temperature may be generated at the guide casing which is held essentially constant for the entire operating time.

To obtain a uniform distribution of the compressed air at the circumference of the guide casing within the air gap, the refinement of the invention is particularly advantageous in which the heated compressed air within the guide roller is distributed by means of a porous sliding casing in an air gap of the air bearing. It is thus possible for the heated compressed air to flow around the hollow cylindrical guide casing in the interior, essentially over the entire length. For this purpose, the porous sliding casing is held at the circumference of the axle support, at which at least one annular chamber which is connected to the compressed air connection is provided. The heated compressed air is supplied, over the entire bearing length extending in the axial direction, to the air gap between the guide casing and the porous sliding casing. This refinement of the invention is characterized in particular in that intensive heating of the guide casing by the heated compressed air is possible. Thus, surface temperatures at the guide casing in the range of 200° C. and higher may be achieved.

The refinement of the invention according to claim 5 and claim 11 is particularly advantageous for conventional air bearings in which the compressed air flows directly into the air gap of the air bearing via nozzle openings. The heated compressed air is distributed within the guide roller via multiple nozzle holes in the air gap of the air bearing. The nozzle openings are advantageously directly provided at the axle support, and are connected to the compressed air connection. The air bearing is formed by an air gap between the guide casing and the axle support.

The invention is particularly suitable for guiding and heating one or more threads within a manufacturing or processing process. The use according to the invention in a melt spinning device, in which one or more threads are guided through multiple godets, heated, and stretched, represents a particular advantage which allows continuous heating of the threads for multiple wrappings on the godets. For this purpose, the multiply wrapped threads are alternatingly heated at the heated surface of the godet casing and at the heated surface of the guide roller. A cooling phase, which is customary in the prior art for conventional guide rollers, is no longer used.

Thus, use of the device according to the invention, in which a godet casing of the godet and the guide casing of the guide roller are heated to the same surface temperature, is particularly advantageous.

Due to the high rotational speeds and low roll resistances of the air-supported guide rollers, the invention may also be used in particular for high thread speeds in the range of 4000 m/min and higher in order to stretch multiple threads in a melt spinning process, for example.

The invention is explained in greater detail below with reference to several exemplary embodiments of the device according to the invention, based on the accompanying figures which show the following:

FIG. 1 schematically shows a side view of a first exemplary embodiment of the device according to the invention for carrying out the method according to the invention;

FIG. 2 schematically shows a side view of another exemplary embodiment of the device according to the invention for carrying out the method according to the invention; and

FIG. 3 schematically shows a view of a melt spinning device for use of a device according to the invention.

FIG. 1 illustrates a first exemplary embodiment of the device according to the invention for carrying out the method according to the invention. A guide roller 1 is shown in a cross-sectional view in the exemplary embodiment according to FIG. 1. The guide roller 1 has a rotatably mounted guide casing 2. For this purpose the guide casing 2 has a hollow cylindrical design. The guide casing 2 is held on an axle support 3 which at one frame end 13 is fastened to a machine frame (not illustrated here). The frame end 13 projects from the guide casing 2 at an end face of the guide roller 1.

The axle support 3 extends essentially over the entire length of the guide casing 2, and an air bearing 4 which passes through the guide casing 2 is provided between the guide casing 2 and the axle support 3.

In the present exemplary embodiment, a sliding casing 7 is situated at the circumference of the axle support 3 to form the air bearing 4. The sliding casing 7 is formed from a porous material, for example an open-pore sintered metal or an open-pore sintering coal. In the overlap region between the sliding casing 7 and the axle support 3, two adjacent annular chambers 6.1 and 6.2 are provided at the circumference of the axle support 3. The annular chambers 6.1 and 6.2 are connected to a compressed air channel 9 via multiple distribution holes 10 which extend radially in the axle support 3. The compressed air channel 9 is provided in the middle region of the axle support 3, and at the frame end 13 opens into a compressed air connection 8.

The sliding casing 7 together with the guide casing 2 forms a circumferential air gap 5, so that compressed air which is supplied to the sliding casing 7 via the annular chambers 6.1 and 6.2 is led through the porous material of the sliding casing 7, and uniformly enters the air gap 5 at the casing surface of the sliding casing 7.

For axially fixing the guide casing 2 to the axle support 3, thrust rings 11.1 and 11.2 are respectively associated with the ends of the guide casing 2. The thrust rings 11.1 and 11.2 are each connected to the guide casing 2 in a rotationally fixed manner. The thrust rings 11.1 and 11.2 are fastened to the guide casing 2 in relation to the end faces of the sliding casing 7 in such a way that radial gaps 12.1 and 12.2 are formed between the respective end faces of the sliding casing 7 and the thrust rings 11.1 and 11.2. The thrust rings 11.1 and 11.2 each have openings in the middle region which connect the radial gaps 12.1 and 12.2 to the surroundings.

The compressed air supplied to the air bearing 4 in the air gap 5 is delivered via the compressed air connection 8 for the guide roller 1. The compressed air connection 8 is connected to a compressed air source 16 via a compressed air line 15. A heating means 14 is associated with the compressed air line 15 for heating the compressed air supplied to the compressed air connection 8. In the present exemplary embodiment, the heating means 14 is formed by a heating coil 17 which heats the compressed air line and the compressed air guided therein. A heat control system 18 which is connected to a temperature sensor 19 is associated with the heating coil 17. The temperature sensor 19 is associated with the compressed air line 15, just before the inlet into the compressed air connection 8.

For the device illustrated in FIG. 1, in the operating state a thread or also multiple parallel adjacently running threads having a partial wrapping is/are guided at the circumference of the guide casing 2 of the guide roller 1. The guide casing 2 is driven to rotation by the thread or threads. For this purpose, compressed air is continuously provided by the compressed air source 16 and supplied to the compressed air connection 8 via the compressed air line 15. The compressed air is heated to a predetermined setpoint temperature by the heating coil 17 before entry into the guide roller 1. The heated compressed air then passes through the compressed air connection 8 and into the compressed air channel 9 of the axle support 3, and via the distribution holes 10 is supplied to the annular chambers 6.1 and 6.2. The heated compressed air then passes through the sliding casing 7 and continuously enters the air gap 5 at the casing surface of the sliding casing 7. An air cushion is thus formed between the guide casing 2 and the sliding casing 7 which extends essentially over the entire length of the air gap 5. The guide casing 2 is heated by the heated compressed air, resulting in a predefined surface temperature, necessary for the thread treatment, at the outer circumference of the guide casing 2.

The heated compressed air which is continuously supplied to the air gap 5 then passes into the surroundings of the guide roller 1 via the radial gaps 12.1 and 12.2. Thus, the bearing of the guide casing 2 and continuous temperature equilibration of the guide casing 2 are achieved at the same time.

To allow a predefined surface temperature to be maintained at the guide casing 2, a heat control system 18 is associated with the heating coil 17. The heat control system 18 is connected to a temperature sensor 19 which continuously detects the temperature of the compressed air which is introduced into the compressed air channel 9 of the axle support 3. If a deviation between a predefined setpoint temperature of the compressed air and a measured actual temperature of the compressed air is determined within the heat control system 18, the heating coil 17 is controlled. In this manner temperature regulation may be provided which ensures a constant compressed air temperature.

FIG. 2 schematically shows a second exemplary embodiment of the device according to the invention. The exemplary embodiment is essentially identical to the previous exemplary embodiment with regard to design and function; therefore, at this point only the differences are explained, and in other respects reference is made to the above description. The components are denoted by the same reference numerals.

For the device illustrated in FIG. 2, the guide casing 2 of the guide roller 1 is mounted directly on the axle support 3. For this purpose, the axle support 3 has a bearing section 31 which is connected at an end face to the frame end 13 which is smaller in diameter. Multiple uniformly distributed nozzle openings 22 are provided at the circumference of the bearing section 31. The nozzle openings 22 are connected via nozzle holes 21 to radially extending distribution holes 10 which open into a middle compressed air channel 9. The compressed air channel 9 is connected at the frame end 13 to the compressed air connection 8.

The air bearing 4 is formed by the radially surrounding air gap 5 between the axle support 3 and the guide casing 2. The air gap 5 extends in the axial direction over the length of the bearing section 31 of the axle support 3; the guide casing 2 has a thrust ring 11.1 and 11.2, respectively, at each end of the bearing section 31. The radially extending radial gaps 12.1 and 12.2 between the axle support 3 and the thrust rings 11.1 and 11.2 are thus formed at the end faces of the bearing section 31.

In the present exemplary embodiment, compressed air is supplied by a compressed air source 16 and a compressed air line 15 which is connected to the compressed air source 16 and to the compressed air connection 8. A compressed air heater 20 which acts as a heating means 14 is connected in the compressed air line 15 in order to heat the compressed air. Thus, the compressed air supplied by the compressed air source 16 is first led into the compressed air heater 20 and heated to a predetermined compressed air temperature. The heated compressed air from the compressed air heater 20 is then supplied to the compressed air connection 8.

A temperature sensor 19 which is associated with the compressed air channel 9 within the axle support 3 is provided for controlling and regulating the compressed air temperature of the heated compressed air. The temperature sensor 19 is connected to the heat control system 18, which is coupled to the compressed air heater 20 for control.

The function of the exemplary embodiment of the device according to the invention for carrying out the method according to the invention, illustrated in FIG. 2, is identical to the previous exemplary embodiment according to FIG. 1, so that further explanation may be dispensed with here.

The exemplary embodiments of the device according to the invention illustrated in FIGS. 1 and 2 are examples of the design of the guide roller 1, and in particular the design of the air bearing 4. It is important that the compressed air supplied to the air bearing 4 is heatable by a heating means situated outside the guide roller. In this regard, the invention is particularly suited for retrofitting guide rollers having cold guide casings which are already installed in machines, so that the compressed air used for the air bearing is supplied to the guide roller in the heated state.

The invention may be used in a particularly advantageous manner in melt spinning devices, in which freshly extruded threads are guided through godet systems, heated, and stretched. FIG. 3 schematically shows one view of an exemplary embodiment of such a melt spinning device. In this regard, only the components of a melt spinning device which are essential for use of the device according to the invention are illustrated. The melt spinning device has a spinning head 23 which bears a spinneret 24 on its underside. The spinning head 23 is connected to a melt source via a melt feed inlet 32. A cooling shaft 25 as well as a godet system having a draw-off godet unit 27 and a stretching godet unit 28 are situated beneath the spinning head 23. The draw-off godet unit 27 is formed by a godet 29.1 and a cold guide roller 30. The godet 29.1 has a heated godet casing 33.

The downstream stretching godet unit 28 is formed by a second driven godet 29.2 and a non-driven heated guide roller 1. A compressed air source 16 and a compressed air heater 20 are associated with the guide roller 1, so that the guide roller 1 according to the exemplary embodiment in FIG. 1 or 2 has a heated guide casing 2. The godet casing 33 of the second godet 29.2 is likewise heated.

In the exemplary embodiment of the melt spinning device illustrated in FIG. 3, a thread 34 is spun from a polymer melt. For this purpose, the polymer melt is extruded through the spinneret 24 into multiple filaments, which are combined into a filament bundle 26 after cooling. The filament bundle 26 is drawn off from the spinneret 4 by means of the draw-off godet unit 27. For this purpose, the thread 34 is wrapped multiple times around the draw-off godet unit 27. The thread 34 is heated by the heated godet casing 33 in order to be stretched by draw-off using the stretching godet unit 28. The thread 34 is likewise guided with multiple wrappings on the stretching godet unit 28, the thread being heated at the surface of the heated godet casing 33 and at the surface of the heated guide casing 2 of the guide roller 1 for thermal aftertreatment. The thread is then wound onto a bobbin or subjected to further treatment, for example crimping for manufacturing a carpet yarn.

The surface temperatures set at the godet casing 33 and at the guide casing 2 are preferably set to be equal in order to heat the thread 34. Thus, for example, for a shrinkage treatment the surface temperature could be in a range of 200° C.

However, the draw-off godet unit 27 together with a driven godet and heated godet casing may also be combined with the device according to the invention. This design is illustrated in dashed lines in FIG. 3.

LIST OF REFERENCE NUMERALS

-   1 Guide roller -   2 Guide casing -   3 Axle support -   4 Air bearing -   5 Air gap -   6.1, 6.2 Annular chamber -   7 Sliding casing -   8 Compressed air connection -   9 Compressed air channel -   10 Distribution hole -   11.1, 11.2 Thrust ring -   12.1, 12.2 Radial gap -   13 Frame end -   14 Heating means -   15 Compressed air line -   16 Compressed air source -   17 Heating coil -   18 Heat control system -   19 Temperature sensor -   20 Compressed air heater -   21 Nozzle holes -   22 Nozzle openings -   23 Spinning head -   24 Spinneret -   25 Cooling shaft -   26 Filament bundle -   27 Draw-off godet unit -   28 Stretching godet unit -   29.1, 29.2 Godet -   30 Cold guide roller -   31 Bearing section -   32 Melt feed inlet -   33 Heated godet casing -   34 Thread 

1. Method for heating a rotatably mounted guide casing of a guide roller for guiding and heating threads, in which the guide casing is held on the circumference of an axle support by means of an air bearing, comprising: heating compressed air outside the guide roller, and supplying the heated compressed air to the air bearing for the guide casing.
 2. Method according to claim 1 wherein heating includes: receiving, in a separate compressed air heater, compressed air from a compressed air source, and applying heat to the compressed air while the compressed air is in the separate compressed air heater.
 3. Method according to claim 1 wherein the compressed air is heated to a setpoint temperature, an actual temperature of the compressed air is detected, and the heating of the compressed air is regulated as a function of a deviation between the setpoint temperature and the actual temperature.
 4. Method according to claim 1 wherein supplying the heated compressed air includes: distributing the heated compressed air within the guide roller by means of a porous sliding casing in an air gap of the air bearing.
 5. Method according to claim 1 wherein supplying the heated compressed air includes: distributing the heated compressed air within the guide roller in an air gap of the air bearing via multiple nozzle holes.
 6. Device, comprising: a guide roller which has a rotatably mounted guide casing and an axle support, an air bearing being provided between the guide casing and the axle support, a compressed air source, a compressed air line, which couples the compressed air source to the air bearing, and a heating means to heat compressed air associated with the compressed air line, the heating means being disposed outside the guide roller.
 7. Device according to claim 6 wherein the heating means is formed by an electric compressed air heater which is connected in the compressed air line between the compressed air source and a compressed air connection for the guide roller.
 8. Device according to claim 6, further comprising: a heat control system, and a temperature sensor for detecting an actual temperature of the heated compressed air, the heat control system and the temperature sensor being associated with the heating means.
 9. Device according to claim 7 wherein the air bearing is formed by an air gap between the guide casing and a porous sliding casing, the porous sliding casing being held at the circumference of the axle support, at which at least one annular chamber which is connected to the compressed air connection is provided.
 10. Device according to claim 9, wherein the porous sliding casing is formed from an open-pore sintered metal or sintering coal.
 11. Device according to claim 7 wherein the air bearing is formed by an air gap between the guide casing and the axle support, the axle support having multiple nozzle openings at the circumference which are connected to the compressed air connection and which open into the air gap.
 12. Device according to claim 6 wherein the guide casing has a hollow cylindrical design and has a thrust ring at each of the two ends, the thrust rings being connected to the guide casing in a rotationally fixed manner and delimiting the air gap of the air bearing toward both end faces.
 13. A method of operating a melt spinning device, including (i) a guide roller which has a rotatably mounted guide casing and an axle support, an air bearing being provided between the guide casing and the axle support, (ii) a compressed air source, (iii) a compressed air line which couples the compressed air source to the air bearing, and (iv) a heating means to heat compressed air associated with the compressed air line, the heating means being disposed outside the guide roller, the method comprising: guiding, heating and stretching one or more threads through multiple godets, at least one of the godets cooperating with the guide roller to guide the thread.
 14. Method according to claim 13 wherein a godet casing of one of the godets and the guide casing of the guide roller are heated to the same surface temperature. 